Fugacity of a gas

Set a constraint for each basis member that you want to include in the calculation. For instance, the constraint might be the total concentration of sodium in the fluid, the free mass of a mineral, or the fugacity of a gas. You may also set temperature (25 °C, by default) or special program options. 

A few gases may be involved in some enzyme reactions, e.g., C02 and 02 as used by carbonic anhydrase and produced by catalase, respectively. If the presence of such dissolved gases affects rates and equilibria at ordinary pressure, their importance will increase at higher pressure. Henry s law says that the partial pressure of a gas above a solution is proportional to its mole fraction in the solution. At high pressure it is more correct to speak of the fugacity / of a gas, instead of partial pressure, in the same sense that one uses activity instead of concentration in solution calculations. In dilute solutions, the fugacity of the dissolved gas is given by... 

Thus, the fugacity of a gas that obeys the Redlich-Kwong equation can be evaluated from the constants a and b at any given pressure P and corresponding molar volume, Vm-... 

The value of the fugacity of a gas in a given state must be calculated by means of an equation of state, either algebraic or graphic it is not determined directly by experimental means. An expression for the fugacity of the fcth substance in a gas mixture can be obtained by comparison of Equations (7.67) and (7.77). These equations give two different ways of expressing the chemical potential, and consequently the two expressions must be equal. Thus,... 

In summary, an experimentally determined equation of state for V leads to a well-defined fugacity for every T and P. If a gas shows ideal behavior to a good approximation (as many gases do for P < 10 atm), the fugacity of the gas is equal to its pressure. This fact, in turn, means that the Standard-State fugacity of a gas is equal to 1 atm, since the Standard-State pressure is 1 atm (Table sl.l). 

Equation (3.51) refers to the general relation between the fugacity of a gas in solution and its concentration. We give fa superscript, w, to indicate that it refers to the water phase. 

The fugacity of a gas in water is usually calculated from measurements of the gas concentration by using the above relation. The concentration of a gas in surface waters is at solubility equilibrium with the atmosphere (saturation) when the fugacities of the atmosphere and water are equal... 

The influence of pressure on the fugacity of a gas at constant temperature is given by equation (29.7) which has bmn used in connection with the determination of fugacities. It is consequently unnecessary to discuss this expression further. 

Hio principle involved in the determination of the fugacity of a gas in a mixture is analogous to that developed in 29b for a pure gas. According to equation (30.17), at constant temperature and composition,... 

Determine by the graphical method the fugacity of nitrogen in the mixture at the various total pressures, and compare the results with those obtained for the pure gases hence, test the Lewis-Randall rule for the fugacity of a gas in a mixture [cf. Merz and Whittaker, J, Am. Chem, Soc., 50, 1522 (1928)]. 

Calculation of the Fugacity of a Gas Using the Peng-Robinson Equation of Stale... 

The fugacity of a gas may normally be calculated if the equation of slate is known. The fugacity coefficient (]) is related to the compressibility factor z, which is given by... 

There is an extremely simple calculation of the fugacity of a gas /, when the gas mixture forms a perfect solution of imperfect gases, because we... 

This relation includes what we call the Lewis equation. This relation is often a very good approximation, especially beyond critical conditions, to calculate the fugacity of a gas mixture from only the fugacity of a pure gas under the same pressure as the total pressure of the mixture. 

RTInp, where p is the pressure. Particularly at higher pressures, gases show very substantial deviations from ideality, but it is often desirable to retain the functional form of the expression for chemical potential, and the fugacity, /, of a gas is defined by the expression p = p°-h P Tin/, where//p - lasp 0, since at low pressure all gases obey the ideal gas law. In principle, the value of p° defined by the fugacity equation is not the same as that... 

Equation 5.9 that would result from such a calculation. It is to make Equation 5.9 apply to all gases by using an effective pressure function specific to each gas in place of the pressure in Equation 5.9. The effective pressure is called the fugacity, and its symbol is/ The definition of the fugacity of a gas is... 

Derive an expression for the fugacity of a gas that obeys Equation 2.29. 

At higher pressures, fugacity can often be calculated by the Lewis rule, which expresses that the fugacity of a gas in a mixture under total pressure P is given by the product of its mole fraction by the fugacity of the same gas at the pure state under the same total pressure hence ... 

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